1. Technical Field
This invention relates to the search technology of a search system using a database that has a forward network structure.
2. Related Art
Conventionally, for example, technology is known relating to a failure diagnosis apparatus for a vehicle, in which a cause and effect relationship is set as a node and a technique is implemented for performing a case search, for example, using a database having a forward network structure in which nodes are connected to each other in a tree structure, such as disclosed in Patent Document 1. With this technique, a so-called “inquiry type” search system is provided to determine the cause by tracing the connections between nodes in response to an input answer of a user to questions about the nodes, which are associated with the tree.
As another example, although it is not a database having a forward network structure such as described above, a retrieval system is provided that represents the elements to be searched by a plurality of vectors and performs a search according to the matching degree with respect to the vector of the search keywords, such as described in Patent Document 2.    Patent Document 1: Japanese Patent Laid-Open No. 62-004663 bulletin    Patent Document 2: Japanese Patent Laid-Open No. 2005-011042 bulletin
However, the conventional technology mentioned above has the following problems. That is, with the technology of Patent Document 1, because it is necessary for a user to reply to questions one by one, this technology is not suitable for immediate decision making, since it takes effort and time to get the desired answers.
In addition, in a case where the user can assume several possible answers to the question content or a case where the user cannot decide on a unique answer, the user must try all of the answers, or at worst follow all of the diverging branches.
In addition, with the technique of Patent Document 2, search results can be obtained instantly by appointing a plurality of search keywords, but there is a problem because the linkage between the elements which are expressed in a vector is judged based only on the distance and the direction of each vector, and this is not suitable for the relation of elements such as answers and results, for example, for the linkage of elements such as “lighting of the HDD trouble lamp” and “trouble of the HDD”.